Countercurrent heat transfer apparatus and method

Abstract

Apparatus for transferring heat between solid particles includes an inclined cylindrical drum in which is disposed a helical auger. The outer lip of the auger, which is maintained in contact with the interior wall of the drum, is curved in the upward direction of the incline axis. The auger blade includes a plurality of apertures of generally uniform size. A feed bin is provided to introduce a first granular material into the upper end of the drum, with the particles of such granular material generally being of a size less than the size of the apertures in the auger blade. A second feed bin is provided to introduce a second granular material into the lower end of the drum, with the particle size of the second granular material generally being greater than the size of the apertures. The drum and auger are rotatable about the incline axis. When rotated, the first granular material sifts through the apertures in the auger blade downwardly in the drum, while the second granular material is forced upwardly by the auger blade. In this manner the first and second materials are placed in contact with one another. Provision of a curved outer lip for the auger facilitates downward movement of the first granular material since the material can move downwardly through the apertures in more nearly a vertical direction. This, in turn, facilitates better counterflow of the first and second granular materials to achieve heat exchange therebetween.

What is claimed is: 
     
       1. A method of transferring heat from one granular material to another comprising introducing into one end of a generally cylindrical drum a first granular material composed of particles of generally a first size and being of a certain temperature,   said drum being positioned so that its cylindrical axis is inclined with said one end of the drum being higher than the other end, a helical auger being disposed in said drum, the flights of said auger including a plurality of apertures having a size which is larger than said first size, the outer lip of said flights being curved toward said one end of the drum,   introducing into said other end of the drum a second granular material composed of particles generally of a second size and being of a temperature different from said certain temperature, said second size being larger than the size of said apertures, and   rotating said auger to move said second granular material upwardly toward said one end of the drum, and to enable sifting downwardly of said second granular material through the apertures in said flights toward said other end of the drum, the first and second granular materials thereby contacting one another to allow transfer of heat therebetween.   
     
     
       2. Apparatus for counterflow heat exchange between first and second granular materials comprising a generally tubular member mounted so that the longitudinal axis thereof is inclined,   a helical auger disposed within said tubular member so that its longitudinal axis is generally coincident with the axis of said tubular member, the flights of said auger having perforations of a size generally larger than the particles of said first granular material and generally smaller than the particles of said second granular material, the outer portion of said flights being formed to extend near the interior wall of said tubular member and to curve in the direction of the incline upwardly,   means for introducing the first granular material into the upper end of said tubular member,   means for introducing the second granular material into the lower end of said tubular member, and   means for causing said auger to rotate so that the auger flights force the second granular material upwardly in the tubular member and so that the first granular material sifts through the perforations in the flights of the auger to move downwardly in the tubular member.   
     
     
       3. Apparatus as in claim 2 wherein the outer portion of said flights is curved so that the first granular material tends to sift vertically downwardly through the perforations in the flights. 
     
     
       4. Apparatus as in claim 2 further including means for causing said auger to vibrate. 
     
     
       5. Counterflow heat exchange apparatus for solids comprising a generally cylindrical drum rotatable about the cylindrical axis thereof, said drum being oriented so that said axis is positioned at an angle with respect to the horizontal,   helical blade means mounted within said drum to rotate as said drum is rotated, the outer lip of said blade means being in contact with the interior wall of said drum, said contact points defining a helix on the interior wall of the drum, said outer lip being curved toward the upper end of said drum, a plurality of apertures being formed in said blade means in the outer lip thereof,   means for introducing into the upper end of said drum a first granular material whose particles are generally of the size to enable passage through said apertures,   means for introducing into the lower end of said drum a second granular material whose particles are generally of a size which would not enable passage through said apertures, and   means for rotating said drum so that said blade means is rotated to move said second material toward and out the upper end of said drum and to allow movement of said first material toward and out the lower end of said drum.   
     
     
       6. Apparatus as in claim 5 wherein said drum is oriented so that said axis is positioned at an angle of from 1 degree to 15 degrees with respect to the horizontal. 
     
     
       7. Apparatus as in claim 5 wherein the cross-sectional profile of the outer lip of said helical blade means at its lowest most excursion is generally disposed horizontally. 
     
     
       8. Apparatus as in claim 5 further comprising means for causing said drum to vibrate to thereby agitate the granular materials and facilitate the passage of said first granular material through said apertures.